Figure 4.

(A) Empirical receiver-operating characteristic (ROC) curves for accuracy of locally predicted tissue ablation over all specimens (n = 12) for each analyzed parameter (dashed lines) and its temporal extremum (solid lines). The curves are generated by plotting the true-positive pixel fraction TPF_tot versus the false-positive FPF_tot of each parameter. The ROC curves allow the relative assessment of each parameter’s ability to classify the lesion. Table 1 lists the corresponding area under the curve (AUC) for each curve shown. (B) Pixel fraction identified as a function of the frame-to-frame decorrelation parameter for pixels in the pre-HIFU region, including all specimens. Because no bubble activity should exist prior to HIFU exposure, this graph was used to propose a threshold for identification of bubble activity of ${\sigma }_{tot}^0=1.22$, where the pixel fraction goes to zero.